Arc start control method in robot welding

Abstract

An arc start control method in robot welding includes the steps of shorting a welding wire with a base metal, retracting a welding torch by a welding robot for taking the welding wire off the base metal to generate an initial arc, retracting the welding torch to a predetermined position with maintaining the initial arc maintained while applying an initial arc current smaller than a steady welding current during this initial arc period, and starting to feed the welding wire steadily and to supply the steady welding current so as to make a transition from the initial arc to a steady arc as well as starting to move the welding torch along a welding line. During a re-shorting prevention period which starts from a beginning of the initial arc period, a re-shorting prevention current which is larger than the initial arc current is applied in order to prevent re-shortening between the wire tip and the base metal right after the initial arc was generated. Thereafter, the initial arc current is applied.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an arc start control method in robot welding for improved arc start in the retract arc starting in which the welding wire is first shorted with the base metal and then the welding torch is retracted by the welding robot to move the welding wire off the base metal to generate an arc.[0003]2. Description of the Related Art[0004]FIG. 5 is a configuration diagram of a robot welder which performs consumable electrode arc welding. A robot controller RC outputs an operation control signal Mc for controlling operation of a multi-axis servo motor disposed in a robot main body (manipulator) RM, as well as sending and receiving interface signals which include a welding start signal St, a feeding rate setting signal Fr, a welding voltage setting signal Vr and a short / arc determination signal Sa, to and from a welding power source PS. The welding power source PS, which receives and sends the interfac...

AI Technical Summary

Benefits of technology

This patent describes a method for controlling the starting of an arc in robot welding to prevent re-shorting and ensure a good start. By applying a high value of re-shorting prevention current right after the initial arcing, the method prevents the wire tip from touching the base metal again, even if there is sudden movement or vibration. The method also allows for adjustment of the arc length during the re-shorting prevention period to further improve the arc starting.

Problems solved by technology

Further, as the robot moves, there is always small vibration, and the welding torch also vibrates during the retracting movement.

Similarly, the vibration of the welding torch also causes an abrupt change in the wire tip position.

The re-shorting does, however; since the initial arc has already made a molten on the wire tip surface, the re-shorting will cause the wire tip to adhere to the base metal.

When this happens, a large electric current of a few hundreds of amperes is necessary in order to break the adhesion, resulting in poor arc start with a large amount of spatters.

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